The three blade trainer prop will work fine. You can also use a two blade 11x6 prop and it will work even better. I have this same engine on my Alpha 40 and used the three blade props until I soloed. Then I switched to 11x6 and 11x7's and performance greatly improved. The three blade props really slow the plane down by design. It just gets expensive replacing them. Just get a 2 1/2", two blade spinner. I like the ones with the aluminum backplates.

Good luck.